Quantum State Engineering in Multi-Level Systems Using Shortcut to Adiabatic Passage

We extend the shortcut to the adiabatic passage method, proposed by Chen et al. [Phys. Rev. Lett. 105, 123003 (2010)], to the creation of an arbitrary coherent superposition of states in a multi-level system. We consider a multi-state system composed of an initial ground state, an excited state and an arbitrary number of final states. In this method, the initial state is linked to the excited state using a pump laser pulse and final states are coupled to the excited state using the Stokes laser pulses. Furthermore, the initial state is coupled to the final states using additional laser fields. We show that the problem can be reduced to the solution of a three-state loop system involving an initial ground state, an excited state and a superposition of final states. This decomposition allows to create an arbitrary coherent superposition of states using the shortcut to the adiabatic passage method. When compared to other strategies, this method provides a fast and robust approach to the coherent superposition of states.